This invention relates generally to a device and technique for positioning a cursor on a cathode ray tube (CRT) or other display device, and more specifically to that type of device referred to as a "mouse" which is moved across a surface to develop a cursor moving signal.
The computer applications where it is necessary to move the cursor are numerous. Word processing and graphics applications are among them. In all such applications, it is desired to move the cursor across the display screen to a new location as swiftly and accurately as possible. When the cursor is at a new location, textual material may be entered into the computer for display at that location, in a word processing application, or graphic symbols may be drawn in reference to that point, in the case of graphics applications.
In many such applications, the basic method of moving the cursor from one location to another involves use of the computer system keyboard, either the standard alpha-numeric characters or the use of special function, cursor moving keys. Other techniques are alternatively utilized, such as cursor movement through an external joy stick or bit pad. These two devices are particularly popular in electronic game applications. Another technique that has been suggested is for a manually operable ball to be held in a rotatable position by an instrument that sits alongside the display device, the operator rotating the ball in the direction and to an extent of the desired cursor movement. Other cursor movement techniques include light or pressure sensitive CRT screens upon which the user moves an instrument to cause the cursor to move.
Another type of device is currently gaining considerable acceptance over these other techniques for many applications. That is to use a "mouse" which is moved by hand over a horizontal surface near the computer or other display device, thereby causing the cursor to move across the screen in accordance with the movement of the mouse. The "mouse" is so named because of its small size, its mouse like movement across a surface and the existence of a cable extending out of one end which looks like a tail. The cable communicates the cursor position signals generated by the mouse to the host computer or other display device. The signals track the user's hand when moving over a horizontal surface adjacent the host computer. The mouse is capable of rapidly moving the cursor from one point to another.
There are two basic types of such mice which are being used or seriously proposed. The first is a mechanical type that utilizes an arrangement of balls or wheels that ride along the horizontal surface as the mouse is moved by hand. The distance and direction of movement is converted by rotation of the balls or wheels into appropriate electrical signals within the mouse, these signals then being used to move the cursor on the host computer display screen. Various forms of this type of mouse are described in U.S. Pat. Nos. 3,541,541; 3,835,464 and 3,987,685.
The second type of mouse uses a periodic optical pattern that is placed on the horizontal surface across which the mouse is moved, an optical detection system being provided within the mouse to determine from the scanned optical pattern the extent and direction of the desired cursor movement. An article entitled "Designing and Testing the Optical Mouse", appearing in VLSI Design, January/February, 1982, pages 20-30, describes optical techniques for determining both direction and extent of mouse movement by purely optical means. This involves the use of a large number of photo-detectors and a complicated algorithm executed by computer software.
It is a primary object of the present invention to provide an improved mouse that is simple in construction, thus trouble free, inexpensive and easy to manufacture, as well as being reliable and easy to use.